Water-insensitive hydraulic fluids containing borate esters

ABSTRACT

A water-insensitive hydraulic fluid composition comprising from about 54.5 to about 92 percent by weight of at least one borate ester, from 0 to about 20 percent by weight of a polyoxyalkylene glycol and from about 3 to about 43 percent by weight of a glycol monoether or diether diluent together with minor amounts of an alkaline buffer and an antioxidant, if desired. Such waterinsensitive hydraulic fluids are high boiling compositions suitable for use as brake fluids.

United States Patent Arthur W. Sawyer Hamden;

David A. Csejka, Orange, both 01 Conn.

Apr. 1, 1968 Dec. 7, 1971 Olin Mathieson Chemical Corporation Continuation-impart of application Ser. No. 653,338, July 14, 1967. This application Apr. 1, 1968, Ser. No. 717,996

Inventors Appl. No. Filed Patented Assignee WATER-INSENSITIVE HYDRAULIC FLUIDS CONTAINING BORATE ESTERS References Cited UNITED STATES PATENTS 3,080,412 3/1963 Young 260/462 3,316,287 4/1967 Nunn et al. 260/462 3,377,288 4/1968 Sawyer..... 252/75 3,414,519 12/1968 Beynon 252/75 Primary Examiner- Leon D. Rosdol Assistant Examiner-D. Silverstein Attorneys-Walter D. Hunter. Donald F. Clements, Thomas P.

ODay, Gordon D. Byrkit, Ellen P. Trevors, Richard S. Strickler and George .1 Koeser WATER-INSENSITIVE HYDRAULIC FLUIDS CONTAINING BORATE ESTERS This is a continuation-in-part of application, Ser. No. 653,338, filed July 14, l967 and now abandoned.

This invention relates to new and improved, water-insensitive hydraulic pressure transmission fluids for use in fluid pressure operating devices such as hydraulic brake systems, hydraulic steering mechanisms, hydraulic transmissions, etc. More particularly, this invention relates to water-insensitive hydraulic fluids which employ as the main lubricant one or more borate esters of glycol monoethers.

One of the basic objects of this invention is to provide hydraulic pressure transmission fluids for use in hydraulic systems which are extremely high boiling compositions and which maintain high boiling points even when water is added to the initial fluid composition. Another object of this invention is to provide a hydraulic pressure transmission fluid having a boiling point of at least about 450 F. A further object of this invention is to provide a hydraulic pressure transmission fluid having a high degree of lubricity while maintaining desired viscosities within a predetermined range under wide variation of temperature conditions.

A great number of hydraulic fluid compositions have been suggested in the art. Commonly, the hydraulic pressure transmission fluids, such as brake fluids are made up of three principal units. The first is a base or lubricant for the system which may include heavy bodied fluids such as polyglycols, castor oil, mixtures of these materials, etc. Diluents, which are employed for the purpose of controlling the viscosity of the fluid as represented by glycol ethers, glycols, alcohols, etc., form the second basic unit. Finally, the third basic unit is represented by an inhibitor system comprising small quantities of inhibitors which are added to reduce oxidation, to improve wetting and flow and to maintain the pH of the hydraulic system above 7 in order to minimize corrosion. Although the hydraulic fluids of the prior art possesses one or more of the desired characteristics of viscosity temperature relationship, volatility, or pour-point, they all suffer from one or more disadvantage and their use is handicapped by the fact that a wide range of suitable properties cannot be obtained. Fluids known in the art are not water insensitive; they suffer from lack of lubricity; some are not stable against oxidation or deterioration; with others it is found that over long periods of use insoluble materials are formed which greatly reduce their efficiency; and in some instances exposure to oxidizing conditions also results in the formation of insoluble compositions. Frequently, it is found that these fluids are also corrosive and that they do not possess the required rubber swelling properties.

It has been discovered that the hydraulic fluids of this inven tion which contain as the main base or lubricant at least one borate ester of a glycol monoether are of low cost; they possess a high boiling point and are essentially odorless and colorless; they possess a high degree of compatibility with other fluids; they exhibit a very low rate of corrosivity; and, especially desirable, they have a high degree of water tolerance.

Another feature of this invention is the highly satisfactory rubber compatibility of the novel fluids as shown in tests carried out according to SAE Standard .l70c. Fluids previously employed have utilized expensive materials such as 2-ethylhexanol, heptanols, butyl ethers of glycols, or diethers of glycols in an amount from about 10 to about 30 percent by weight of the total composition to achieve the desired rubber swelling characteristics. The rubber swelling properties of the fluids of this invention are derived from the lubricant or base portion. The importance of the rubber swelling properties of the fluid cannot be overlooked since too little swelling will result in leakage of the fluid past the rubber cup sealing means and past the piston in hydraulic cylinders with corresponding loss of power. On the other hand fluids which cause too much rubber swelling are not desirable in that they destroy the structural properties of the rubber sealing cups in hydraulic cylinders, in turn, results in malfunction or inoperativeness of the unit.

Lubricant or Base Compositions The lubricant or base compositions employed in the novel hydraulic fluids of this invention comprise at least one borate ester of a glycol monoether as the main base or lubricant and, optionally, may contain a minor amount of a polyoxyalkylene glycol having a molecular weight of not less than 150. From about 54.5 to about 92 percent by weight of the final fluid will consist of the borate ester and from 0 to about 20 percent of a polyoxyalkylene glycol will be present in the final fluid, the percent by weight being based on the total fluid weight. Preferably, from about 60 percent to about 90 percent by weight of the final fluid composition will be the borate ester compound or compounds while 0 to about 10 percent by weight of the final fluid composition will be the polyoxyalkylene glycol or mixture of polyoxyalkylene glycols. The polyethylene glycols represent a preferred group of polyoxyalkylene glycols.

A wide range of polyoxyalkylene glycols can be employed in the lubricant or base compositions of this invention. Useful polyoxyalkylene glycols include those having molecular weights ranging from not less than about 150 to about 400, and preferably from about 200 to about 350. Suitable polyoxyalkylene glycols include polyethylene, polypropylene and polybutylene glycols.

Although a wide variety of borate esters can be employed as lubricants in the novel hydraulic fluids of this invention, an especially useful class of borate esters are the so-called triborate esters of glycol monoethers having the general formula:

wherein R is a lower alkyl radical containing from one to four carbon atoms, x is an integer from 2 to 4 inclusive and y is an integer from 2 to 4 inclusive. Borates of the above-mentionedtype include, for example, (CH (OCH CH O) -,-B, 2 5( z 2)a )a a 1( 2 2)4 )a- (CH,,(OCH HCl-l O) -B, (CH:,(OCH CHCl-l O) B, z 5( z a)t (s' (C4H9(OCH2CHCH3)40)3 B (C H-,(OCH,CHCH;,) ,O) B, and (CH (OCH CHCH ),O) B.

Borates of the above-mentioned type can be conveniently prepared by reacting orthoboric acid and the glycol monoether while in the presence of a water-azeotrope forming solvent. Water formed in the esterification reaction is continuously removed as the azeotrope. At first, the temperature of the reaction mixture is maintained between about 0 C. and about l90 C. and desirably at the distillation temperature of the water-solvent azeotrope. After essentially complete removal of the water formed during the esterification the excess solvent is conveniently removed from the reaction mixture by distillation. The borate ester product, which is left in a residue, may then be recovered by distilling under reduced pressure or by extraction with a suitable solvent followed by evaporation of the solvent. For example, the compound (C H (OCH CH O) B can be prepared by reacting 2 moles of C H,,(OCH CH OH, 0.67 mole of orthoboric acid and 700 ml. of ethylbenzene with heating and mixing to yield 198 grams of the ester, a water-white liquid boiling at 222-22 3 C. (5 mm. Hg). The preparation of the esters of this type is more completely described in US. Pat. No. 3,080,4 l 2.

A second highly useful class of borate esters includes compounds of the general formula:

wherein R, and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20 and R, is alkyl of from one to four carbon atoms and with proviso that one of R and R is [Cl-i (OCl-l Cl-l (OCH CHCl-l )O] B [C H,,(OCH CHCl-la) -(OCH Cl-l )O] -B [C H (OCH,CHCH --(OCl-i Cl-l )O] B [C,H,,(OCH Cl-l -(OCl-l Cl-lCl-l )O] B a( z z')u( 2 a)s ]a z s( z' u)12( 2 2)a ]a a 7( 2 a)|o z 2)io Another class of borate esters useful'in the fluid compositions of this invention include esters having heteric oxyalkylene chains, that is, oxyalkylene chains in which oxyethylene and oxypropylene units are distributed randomly throughout the chain. These type III esters have the general formula:

Rg represents a heteric oxyalkylene chain having the formula:

where the sum of r and s is not more than 20 and wherein the weight percent of oxyethylene units in the said chain is not less than 20 based on the total weight of all the oxyalkylene units in the chain and R is alkyl of from one to four carbon atoms. The preparation of type III esters can be accomplished in the same general manner as the preparation of types I and ll described above by reacting orthoboric acid in the presence of toluene with a heteric glycol monoether of the formula:

J SI Where R, and Rg have the same meaning as previously set forth. Glycol monoethers of this class can be conveniently prepared by methods well known in the art such as the process described in U.S. Pat. No. 2,425,845.

A fourth type of borate esters suitable for use in the fluid compositions of this invention have the general formula:

C'ERQE O ('RtCHCHaO)n-(RaCHCHaQ)mT| wherein T T and T are each an independently selected alkyl group having from one to four carbon atoms, R.,, R R R R andR, are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same.

Borate esters of this type can be prepared in the same way as the process described for type I esters previously mentioned.

Type IV borate esters suitable for use in the fluids of this invention include, for example:

Diluents The diluent portion of the novel fluid composition of this invention can constitute from about 3 to about 43 percent by weight based on the total weight of the fluid composition of one or more diluents which are glycol monoethers, or diethers of the formula: I

' I ZLL wherein R is alkyl from one to four carbon atoms, R is hydrogen or alkyl of from one to four carbon atoms, x is an integer from 2 to 4, and y is an integer from 2 to 4. Preferably,

the hydraulic fluid composition will contain from about 6.5 to about 35 percent by weight, based on the total weight of the fluid composition, of the glycol monoether or diether. Useful glycol monoethers and diethers, many of which are commercially available include, for example, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-butyl ether, tetrapropylene glycol monomethyl ether, dibutylene glycol monomethyl ether, tributylene glycol monon-propyl ether, tetrabutylene glycol mono-n-butyl ether and the corresponding diethers thereof. Additives When desired, inhibitors for pH and corrosion control, such as alkaline inhibitors as exemplified by the alkali metal borates, can be employed in an amount sufl'icient to maintain alkaline conditions in the fluid compositions, e.g., a pH value of from about 7.0 to about 1 1.5. These inhibitors are generally added in an amount of from about 0.5 to about 5.0 percent by weight based on the total weight of the fluid composition and preferably from about 0.8 to about 5.0 percent by weight on the same basis. Useful inhibitors include alkali metal borates, such as sodium borate, potassium tetraborate, etc.; sodium meta arsenite; alkali metal salts of fatty acids, such as potassium oleate, the potassium soap of rosin or tall oil; alkylene glycol condensates with alkali metal borates, such as the ethylene glycol condensate of potassium tetraborate; amines, for example, ethanolamine, methyl diethanolamine, diethanolamine, di(2-ethylhexyl) amine, di-N-butyl amine, monoamyl amine, diamylamine, dioctylamine, salicylal monoethanolamine, di-B-naphthyl-p-phenylene diamine, N,N-disalicylidenel ,Z-propanediamine, N,N-disalicylal ethylene diamine, dicyclohexylamine, and amine salts such as monoor dibutyl ammonium borate; phosphites, such as triphenyl phosphite, tri(tert amylphenyl) phosphite, diisopropyl phosphite, etc.; mercaptobenzotriazole; morpholine compounds including alkyl morpholines having from one to four carbon atoms in the alkyl group such as N- ethyl morpholine, N-isopropyl morpholine, N-butyl morpholine; N-phenyl morpholine, N-( 2-aminoethyl) morpholine, N-( 2-hydroxyethyl) morpholine, etc.,

phosphates, including the alkali metal phosphates, dibutyl amine phosphates, the dialkyl acid o-phosphates and amine salts thereof; triazoles including benzotriazole, 1,2- naphthotriazole, 4-nitrobenzotriazole, aminobenzotriazoles such as S-acylamino benzotriazole, and alkyl triazoles having one to 10 carbon atoms in the alkyl group as exemplified by methyl triazole, ethyl triazole, n-propyl triazole, tertiary butyl triazole, hexyl triazole, isodecyl triazole, etc. Other useful corrosion inhibitors include adenine, 4-methylimidazole, 3,5- dimethyl pyrazole, 6-nitroidazole, imidazole, benzimidazole, guanine, indazole, ammonium dinonylnaphthaline sulfonate, dioleyl thiodipropionate, ethylbenzoate, ethyl-paminobenzoate, cyclohexyl ammonium nitrite, diisopropyl ammonium nitrite, butynediol, l,3,5-trimethyl-2,4,6-tris (3,5-

di-tert. butyl-4-hydroxybenzoyl), 4,4'-methylene bis(2, 6-di ten. butylphenol), 4-hydroxymethyl-2,6-di-tert. butylphenol tion contain from about 0.00] to about 1.0 percent by weight of an antioxidant based on the total weight of the fluid composition, to protect the diluents. Typical antioxidants include phenolic compounds, such as 2,2-di-( 4-hydroxyphenyl) propane, phenothiazine, phenothiazine carboxylic acid esters, N-alkyl or N-arylphenothiazines, such as N-ethyl phenothiazine, N-phenyl phenothiazine, etc.; polymerized trimethyldihydroquinoline; amines, such as phenylalphanaphthylamine, phenyl-betanaphthylamine, N,N'-dioctyl diphenylamine, N,N-di-B-naphthyl-p-phenylene diamine, p-isopropoxy diphenylamine, N,N-dibutyl-p-phenylene diamine, diphenyl-p-phenylene diamine, N,N-bis(l,4- dimethylpentyl)-p-phenylene diamine, N,N-diisopropyl-pphenylene diamine, p-hydroxydiphenylamine, etc.; hindered phenols such as dibutyl cresol, 2,6-dimethyl-p-cresol, butylated 2,2-di-(4-hydroxyphenyl) propane, n-butylated aminophenol, butylated hydroxyanisoles, such as 2,6-dibutylp-hydroxyanisole; anthraquinone, dihydroxyanthraquinone, hydroquinone, 2,5-di-tertiarybutylhydroquinone, Z-tertiary butylhydroquinone, quinoline, p-hydroxydiphenylamine, phenyl benzoate, 2,6-dimethyl p-cresol, p-hydroxyanisole, nordihydroguaiaretic acid, pyrocatechol, styrenated phenol, polyalkyl polyphenols, sodium nitrite, etc. Mixtures of the above-mentioned antioxidants can be employed, if desired. It should be emphasized that with a variety of the fluids of this invention, which are suitable for a wide range of industrial application, a separate antioxidant is not required.

Formulation of the novel fluid of this invention is accomplished by blending the components to a homogeneous stage in a mixing vessel. The preferable blending temperature is from about 50-l25 F. It is preferable to warm the solution during preparation to facilitate dissolution. The blending of the compounds is conveniently conducted at atmospheric pressure in the absence of moisture.

in general, any suitable method can be used in preparing the liquid compositions of this invention. The components can be added together or one at a time, in any desired sequence. It is preferable, however, to add the antioxidant and alkaline inhibitor as a solution in the glycol ether component. All components are mixed until a single phase composition is obtained.

The following examples which illustrate various embodiments of this invention are to be considered not limitative:

EXAMPLE 1 Percent by Weight lCH,(0CH,CH,).1O],-B 67.39 Triethylene glycol monomethyl ether 23.20

Diethanolurnine 1.78 Polyethylene glycol (M01. wt. 300) 7.62 Sodium Nitrite 0.01

EXAMPLE 11 Percent by Weight [CH,(0CH,CH,),O],B 89.48 Triethylene glycol monomethyl ether 6.68 Polyethylene glycol (Mol. wt. 300) 1.83 Methyldiethanolumine 1.99 Sodium Nitrite 0.02

The reflux boiling point 1 of the above fluid was measured and found to be 552 F. at atmospheric pressure. To test the water insensitivity of the fluid composition of example 11 a composition consisting of 100 parts by volume of the fluid plus 3.5 parts by volume of water was prepared and it was found to have a reflux boiling point at atmospheric pressure of 402 F. indicating that the fluid is exceptionally water insensitive. For example, when a conventional brake fluid which boils above 500 F. is tested in the same manner, the reflux boiling point drop is about 250 F. or more.

, All reflux boiling point measurements in this example and in the other examples of this specification were conducted in accordance with the procedure of SAE Standard J70c.

EXAMPLE 111 Percent by Weight l H.( .).1 11- no.0 Triethylene glycol monomethyl other 2 9 N-ethyl morpholine 4 4 Polyethylene glycol (Mol. wt. 300) 7.7

The reflux boiling point of this field was measured and found to be 440 F. at atmospheric pressure. On addition of 3.5 parts by volume of water to parts by volume of the fluid there was obtained a fluid having a reflux boiling point at atmospheric pressure of 353 F. When tested according to the procedure of SAE Standard J70c, this fluid passed the evaporation requirement for SAE heavy duty type 70R3brake fluid.

EXAMPLE 1V Percent by Weight [C";(OCH3CHI)1\0]:|'B 67.04 Triethylene glycol monomethyl ether 21.72 N-phenyl morpholine 1.89 Diethanolamine 0.85 Polyethylene glycol (Mol. wt. 300) 8.50 Properties Reflux boiling point at atmospheric pressure 498 F.

Reflux boiling point at atmospheric pressure of 3.5

parts by volume of water and 100 40 F. 1.620 cs.

2l2 F. 2.74 cs.

Water Tolerance Test Pulsed water tolerance test at -40 F. and F. according to procedure of SAE J70c.

EXAMPLE VI Percent by Wei ht LQs s(9. jzc HQ Ql i 82.7 Triethylene glycol monoethyl I ether l0.00 Methyldiethanolamine 2.20 Polyethylene glycol (Mol. wt. 300) 5.00 Sodium nitrite 0.02 Properties Reflux 'boiling point at atmospheric pressure 554 F.

Reflux boiling point at atmospheric pressure of 3.5 parts by volume of water and parts by volume of fluid of example VI 383 F. Viscosity 40 F. 1,9l0 cs. 2l2 F. 2.82 cs.

Water Tolerance Test Passed 40 F. and I40 F. water tolerance test according to procedure of SAE J70c.

EXAMPLE VII Percent by Weight lCH,(OCl-l,CH,),O],'B 70.13 Triethylene glycol monomethyl ether 20.00

Diethanolamine 1.86 Triethylene glycol (Mol. wt. 150) 8.00 Sodium nitrite 0.0]

Properties Reflux boiling point at atmospheric pressure 500 F. Reflux boiling point at atmospheric pressure of 3.5 parts by volume of water and I00 parts by volume of fluid olexample Vll 38l F. Viscosity -40 F. 2.050 cs.

Zl2 F. 2.80 cs. Corrosion Test Passed corrosion test according to procedure of SAE 170:. Water Tolerance Test Passed water tolerance test at -40 F. and 140 F. according to procedure of SAE .l70c.

EXAMPLE VIII Percent by Weight [C.H,(OCH,CH,),O|,-B 28.29 (CH,(OCH,CH,) OI,-B 55.58 Triethylene glycol monomethyl ether 8.05 Polyethylene glycol (Mol. wt. 300) 6.ll Methyldiethanolamine l .94 Sodium nitrite 0.03 Properties Reflux boiling point at atmospheric pressure 562 F. Reflux boiling point at atmospheric pressure of 3.5 parts by volume of water and I00 parts by volume of fluid olexample Vlll 400 F.

Viscosity 40 F. 2.540 es. 212' F. 3.27 cs.

Water Tolerance Test Passed water tolerance test at 40' F. and H0 F. according to procedure of SAE J70c.

EXAMPLE lX Reflux boiling point at atmospheric pressure of 3.5 parts by volume of water and I00 parts by volume of fluid of example IX Viscosity 40 F. 1,470 cs.

2l2 F. I 2.64 ea. Water Tolerance Test Passed water tolerance test at 40 F. and l40 F. according to procedure of SAE J70c.

Borate Ester D employed in the above fluid, which is an example of a type IV ester, was prepared in the following manner: One mole (61.8 grams) of orthoboric acid was added to a solution of one mole (164 grams) of triethylene glycol monomethyl ether and 50 ml. of toluene. The mixture was heated to the boiling point and one mole l8 ml.) of water was removed as the azeotrope with toluene. The solution was cooled slightly below the boiling point and one mole (l34 grams) of diethylene glycol monoethyl ether was added. Heating was resumed until another mole (18 ml.) of water was removed from the reaction mixture. Again the solution was cooled below the boiling point and one mole grams) of diethylene glycol monomethyl ether was added. The solution was heated to boiling and a third mole (l8 ml.) of water was removed following which the toluene remaining in the reaction mixture was removed to yield a tri borate ester of the formula:

The boiling point of the ester was 610 F. at atmospheric pressure and it exhibited a viscosity of 775 cs. at -40 F.

Properties Reflux boiling point at atmospheric pressure 555 F. Reflux boiling point at atmospheric pressure of 3.5 parts by volume of water and 100 parts by volume of fluid of example X 383 F.

Borate Ester E employed in the above fluid composition, which is a type III borate ester, was prepared as follows: One mole (354 grams) of a random addition product of ethylene oxide and propylene oxide with butyl alcohol, prepared by reacting a mixture containing 50 weight percent ethylene oxide and 50 weight percent propylene oxide with the alcohol, and 60 ml. of toluene were mixed with one-third mole (20 grams) of orthoboric acid. The mixture was heated to its boiling point and one mole 18 ml.) of water was removed as the azeotrope with toluene after which the toluene remaining in the reaction mixture was removed under vacuum. The resulting tris borate ester (Borate Ester E) was clear, water-white liquid having a boiling point of approximately 625-30 F.

EXAMPLE XI Percent by Weight lC,H,(OCH,CH,),0],-B 80.00 Triethylene glycol monoethyl ether 12.78 Mcthyldiethanolamine 2.20

Polyethylene glycol (Mol. wt. 300) 5.00 Diisopropyl ammonium nitrite 0.02

EXAMPLE XII Percent by Weight I =(OCH= =).1 ls-B 70.30 Triethylene glycol monomethyl ether 19.95 Diethanolamine 1.85 Polyethylene glycol (Mol. wt. 300) 7.85 Di(2ethylhexyl) ammonium nitrite 0.05

EXAMPLE XIII Percent by Weight 1CH,(OCH,CH,),O],-B 66.00 Triethylene glycol monomethyl ether 25.90 Diethanolamine 1.85 Polyethylene glycol (Mol. wt. 300) 6.00 Benzotriazolc 0.25

EXAMPLE XIV Percent by Weight l 1 .5( g). oi3B 80.00 Triethylene glycol monoethyl ether 15.0 Polyethylene glycol (Mol. wt. 300) 5.0

EXAMPLE XV Percent by Weight l s( 1 r)=| 1.1- 67.40 Triethylene glycol monomethyl ether 25.111 Diethanolamine 1.78 Polyethylene glycol (Mol. Wt. 300) 5.00 Sodium nitrite 0.0l

EXAMPLE XVI Percent by Weight I H,( -1, n 1.4! 75.00 Triethylene glycol monomethyl ether 6.20 Tetraethylene glycol monoethyl ether 17.00 Diethanolamine 1.68 Sodium nitrite 0.02 Tolutriazole 0.10

The fluid composition of Example XVI was tested according to the procedures set forth in Motor Vehicle Brake Fluid SAE Standard 11703. Pertinent data which illustrates the outstanding properties of this fluid is shown below:

PROPERTIES OF WATER INSENSITIVE BRAKE FLUID OF EXAMPLE XVI Test SAE J 1703 Test Results Boiling Point 374 min. 532 F. Flash Point l79.6 F. min. 320 F. Viscosity at 212 F. 1.5 cs. min. 2.5 cs. Viscosity at 40 F. 1,800 cs. max. 1.530 cs. pH 7.0 to 11.5 7.5 Evaporation Loss percent max. 62 percent EXAMPLE XVII Percent by Weight [CH ,(OCH,CH,) O] -B 70.00 Tetraethylene glycol monoethyl ether 21.00 Triethylene glycol monomethyl ether 7.20 Diethanolamine 1.68 Tolutriazole 0.10 Sodium nitrite 0.20

Reflux boiling point at atmospheric pressure 528 F. Viscosity at 40 F. 1,447 cs. pH 7.3

EXAMPLE XVIII Percent by Weight ICH,(OCH,CH .O l -B 70.00 Tetraethylene glycol monoethyl ether 25.00 Triethylene glycol monomethyl ether 3.20 Diethanolamine 1.68 Tulutriazole 0.10 Sodium nitrite 0.02

Reflux boiling point at atmospheric pressure 528 F. by Weight Viscosity at 40 F. L552 cs.

H 7.35 p cn rocmcu, no 1.4; 66.00

Triethylene glycol monoethyl ether 5.00 XIX Triethylene glycol monornethyl ether 17.00 Tctrnethylene glycol monomethyl Percent ether l0.00 by weighl Diethyl amino ethanol 2.00

ICHI(OCHICHI).!OIS'B 6600 EXAMPLE XXV Tetraethylene glycol monoethyl I ether 29.00 Triethylene glycol monomethyl ether 3.20 Percent Diethanolamine 1.68 15 by Weight Tolutriazole 0. l 0 Sodium nitrite 0.02

Reflux boiling point at atmospheric {C.Ha(oCHCH)0h B 7100 Diethylene glycol monoethyl pressure 526 F. m s 00 Viscosity a: -40 F. 1.5m cs. F

H 75 Tnethylene glycol monomethyl p ether l0.00

Tetraethylene glycol monomethyl ether [0.00 EXAMPLE XX Dimethyl amino ethoxyethanol 2.00

EXAMPLE XXVI by Weight lCH,(OCH,CH,),O|,-B 75.00 Percent Tetraethylene glycol monoethyl by Weight ether 23.20 Diethanolamine 1.68 Tolutriazole 0. l0 )a ln 7 Sodium "mile Q02 Triethylene glycol monomethyl Reflux boiling point at atmospheric pressure F' Tetraethylene glycol viscoshy a l 663 monomethyl ether l5.00 Diethanolamine 1.78 Sodium nitrite 0.02

EXAMPLE XXI EXAMPLE XXVII Percent by Weight Percent by Weight |CH,(0CH,CH,),0],-B 75.00 T ieth l I col m eth l g y y I L25 cH. oc|-|,cH, .o1.-B 7.500 Tetraethylene glycol monomethyl Tnelhylene glycol monomethyl ether 12.00 F'T' I l h l Diethyl amino ethoxyethanol 1.75 y em: 8 yco mono y ether 7.00 Tetraethylene glycol monoethyl ether l0.00 EXAMPLE Hydroxyethyl hydrazine 1.90 Tolutriazole 0.10 5 0 Percent by Weight EXAMPLE XXVlll flOCHfiHzhOh-B 70.00 Triethylene glycol monomethyl Percent ether l3.25 by Weight Tetraethylene glycol monomethyl ether 15.00 Methyl diethanolamine L75 [CH-1(oCH1CHl 71-00 Triethylene glycol monomethyl ether l8.00 XX"! Tetraethylene glycol monomethyl ether 9.00 Diethnnolamine 1.93 Sodium nitrite 0.02 Percent Benzotriazole 0.05 by Weight EXAMPLE XXIX lCH,(OCH,CH,),O],-B 72.00 Triethylene glycol monoethyl ether l6.25 Tetraethylcne glycol monoethy Percem ether l0.00 by wcigm Hydroxyethyl hydrazine l.75

[C H,(0CH,CH,) O],-B 75.00 EXAMPLE xxlv Triethylene glycol monomethyl ether 6.00 Triethylene glycol monoethyl ether 7.00 Percent Tetraethylene glycol monoethyl ether i0.00 T t Hydroxycthyl hydrazine 1.90 i f f j Tolutriazole 0. l Sensitive SAE 70R3 fluid of Test specification Example I EXAMPLE XXX Fluidity and appearance:

(Cold test) 40 F., six days:

Black contrast lines, HP chart. percem Stratification-sediinontation None None b Wei m Air bubble travel time (max.) sec... 2

y 58 F., six hours:

10 gtlacgficorgrast 12111108, Illflohart. N N

ra ca on-se men a on. one one P Air bubble travel time (main) sec.-. 36 5 Triethylcnc glycol monomelhyl Evaporation test:

690 Percent loss (main) percent 69 Triethylene lycol monoethyl Gritty or abrasive residue. None None ether 7.00 Pour point (main) "F 23 23 Tciraethylenc glycol mnnoethyl 5 fig g gf ou g m lh '28 Bla k contrast lines, HP chart. Y Stratiflcation-sedimentation. None None 010 Air bubble travel time (main) sec... 10

140 F., 24 hours:

Stratification None None Sedimentation. percent by vol. C tiMutitlt.) 0.05 0. 01

om a EXAMPLE XXXl 40 F., ii hours:

Black contrast lines, HP chart Stratification-sedimentation. None None 140 F., 24 hours: omen, gtr o tliica tian 0 None None 9 men 8 on, IJGI'CGH V0 by 25 (max.) 0. on 0.01

Resistance to oxidation (Peroxide test): iffilflilfilffii f None None r py a y dimclhyl Cast ironmn None None Weight loss in mgJsq. cm.: N-ethyl mo pholinc Aluminum alloy (max. 0. 05 0.00 Polyethylene glycol Cast iron (max.).. 0. 30 +0. 01

(MOL wt 25 7 Efiect on rubber-458 F Hardness decrease, deg.:

Natural (max.) 10 2 SEE (max.) 10 3 Base diameter increase, in.:

Natural 0. 006-0. 055 0. 013 SBR 0.006-0.055 0.0i9 Disintegration rubber cups None None Efiect on SBR rubber-248 F.: i The fluid composition of example i was tested according to Igardness decrease (max-l deg 0W 0 ase diameter increase, in 0. 0. 055 the procedures set forth in Hydraulic Brake Fluid SAE Stan Disintegration rubber cups None None dard J 700 for heavy duty types 70Ri and 70R3 hydraulic Specific gravity 60/60 F 1. 085

. o a o O brake fluid. Pertinent data relating to these tests, which illus- 40 ggi i per @110" trates the outstanding properties of these novel fluids, is shown in table 1. The fluid of example i was found to satisfy 28232 dlscermblecompletely the requirements for SAE heavy duty type 70R3 a straw hydraulic brake fluid. The fluid of example ll, which was 7 tested according to the procedures of J 70c for water tolerance and evaporation, was found to pass both of these tests.

TABLE 1.-PROPERTIES OF WATER INSENSITIVE BRAKE FLUID OF EXAMPLE I [Tests conducted according to procedures set forth in Society of Automotive Engineers Standard J70c] TABLE 1.EFFECT OF ADDED WATER ON BOILING POINT Test results 5 5 Reflux boiling point, F.

water insensitive Water insensi- SAE 7OR3 fluid oi Conventional tive fluid of Test specification Example I Water, percent by vol. Fluid Example I Boiling point min) r 314 484 497 Flash point (min) F 179 & 380 v 450 Viscosity: 294 373 40 F. (max) cs. 1,800 122 F. (min) cs 4, 2 7, 34 3.5 ml. H O/100 ml. brake fluid. 212 F. (min.) cs 1.5 2. 71 pH. 1-11. 6 7. 70 Nora-The composition oi conventional Fluid A was as follows: Stability at high temperature: 7

Boiling point (min.) "F 374 495 weight Boiling point change (male) F.. 5:9. 0 2 Percent Corrosion test (wt. change mg./sq. cm.)

opper 0. 4 -0 18 A 60-50 weight percent ethylene oxide-propylene oxide Brass.- 0. 4 0. 14 random addition reaction product with butyl alcohol Cast iron 0.2 +0, 01 (ave. mol wt. 1,000) 20. 0 Aluminum alloy 0. 1 0, 00 Trietliylene glycol monomotliyl at 19. 0 Steel 0, 2 0, 00 Triethylene glycol monoetliyl other. 2 T ned iron 0, 2 0, 00 'iriethyleno glycol inonobutyl other. 19. Sedimentation, percent by vol. (ma 0.10 0. 01 Ethylene giyeol 1.5 Jelling fluid/water mixture None N Diphcnyiol propuiio. v. 0. i Crystalline deposit jar walls or strips... Nom- No Condensate oi 7 moles ethylene glycol with 1 mole of pH fluid/water mixture 7-1i 5 7, potassium tetriilmriite Rubber cups: Swelling (max.) in 0 055 0 007 Total 100. 0 Softening (ma e) deg 1 -3 75 TABLE l.-PROPERTIES OF WATER INSENSITIVE BRAKE FLUID OF EXAMPLE I Simulated service performance procedure N0. 2 (85,000 strokes; 248 F/ Test results water insensitive SAE 70R3 fluid of Test specification Example I Corrosion of metal parts as evidenced by discernible pitting None None Change in initial diame piston (max.) 0.005 None Lip diameter interference set rubber cups,

percent:

Wheel cylinder cups (max) 65 7. 2 Master cylinder on s:

Primary (max. 65 7. 2 Secondary (max.) 65 0. Hardness decrease-of rubber cups, deg;

Wheel cylinder cups (max.) 15 4 Master cylinder on 5:

Primary (max. 6 Secondary (max) 15 5 Operating condition of rubber cups as evidenced by excessive tackiness, scoring, scuffing, blistering, cracking, chipping, or change in shape Fluid loss during any 24,000 st (main) in 36 7 Freezing or malfunction of cylinder pistons. None None Gum deposited on metal parts of cylinder walls that are abrasive or cannot be re moved with ethanol 1 None Deposit formed or adhering to cylinder walls that are abrasive or cannot be removed with ethanol None None Fluid loss during 100 strokes at end of test (main) ml 36 5 Condition of fluid and brake cylinders by evidence of sludging, gelling or grittiness likely to cause improper brake action. None None Percent sediment in fluid drained from wheel cylinders, 72 hours equilibrium (men) 1.5 0. 5 Percent sediment in fluid drained from cylinder, 72 hours equilibrium (max.) 1. 5 0. 05 Decrease in base diameter of rubber cups, in.

Wheel cylinder cups (max.) 0. 035 0. 020 Master cylinder cu s:

Primary (max. 0. 035 0. 025 Secondary (max) 0. 035 0. 035

' Satisfactory. 2 Trace.

What is claimed is:

l. A hydraulic fluid composition consisting essentially of (A) from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition, of at least one base or lubricant selected from the group consisting of (a) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a boratc ester of the formula:

wherein R, is alkyl of from, one to four carbon atoms, R, and- R, are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R, and R is methyl and one of R and R is hydrogen; (c) a borate ester of the formula:

Ram n-B,

wherein R, is alkyl of from one'to four carbon atoms, Rg is a heteric oxyalkylcne chain of the formula:

wherein the sum of r and s is not more than and wherein the weight percent of the oxycthylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a boratc ester of the formula:

wherein T,, T, and T are each an independently selected alkyl group having from one to four carbon atoms; R R,,, R,,, R R,

and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; (B) from 0 to about 20 percent by weight based on the total weight of the fluid composition of a polyoxyalkylene glycol having a molecular weight of not less than and up to about 400, and (C) from about 3 to about 43 percent by weight based on the total weight of the fluid of at least one diluent having the formula:

wherein R is alkyl of from one to four inclusive carbon atoms, R is selected from the group consisting of hydrogen and alkyl of from one to four inclusive carbon atoms, at is an integer of from 2 to 4 inclusive and y is an integer'of from 2 to 4 inclusive.

2. A hydraulic fluid composition consisting essentially of (A) from about 54.5 to about 92 percent by weight, based on the total weight of thc fluid composition of at least one base or lubricant selected from the group consisting of (a) borate ester of the formula: I

wherein R, is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a boratc ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, R, and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R and R is methyl and one of R and R is hydrogen; (c) a boratc ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula:

wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylcne units is not less than 20 based on the total weight of all the oxyalkylcnc units; and (d) a borate ester of the formula:

wherein T,, T and T are each an independently selected alkyl group having from one to four carbon atoms; R R,, R R-,, R,

and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20 and with the proviso that in no more than two of the chains is the sum of n and m the same; (B) from 0 to about 20 percent by Weight, based on the total weight of the fluid composition, of a polyoxyalkylene glycol having a molecular weight of not less than 150 and up to about 400, (C) from about 3 to about 43 percent by weight, based on the total weight of the fluid, of at least one diluent having the formula:

wherein R is alkyl of one to four inclusive carbon atoms, R is selected from the group consisting of hydrogen and alkyl of from one to four inclusive carbon atoms, x is an integer of from 2 to 4 inclusive, and y is an integer of from 2 to 4 inclusive and (D) from about 0.5 to about 6.0 percent by weight, based on the total weight of the fluid of an inhibitor for pH and corrosion control.

3. The hydraulic fluid composition of claim 2 wherein the said base or lubricant is:

4. The hydraulic fluid composition of claim 2 wherein the said polyoxyalkylene compound is polyethylene glycol having a molecular weight of 300. v

5. The hydraulic fluid composition of claim 2 wherein the said diluent is a mixture of triethylene glycol monomethyl ether and tetraethylene glycol monoethyl ether.

6. The hydraulic fluid of claim 2 wherein the said inhibitor is N-ethyl morpholine.

7. The hydraulic fluid composition of claim 2 wherein the said inhibitor is a mixture of diethanolamine and tolutriazole.

8. A hydraulic fluid composition consisting essentially of (A) from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition of at least one base or lubricant selected from the group consisting of (a) borate ester of the formula:

' wherein R, is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a borate ester of the formula:

v wherein R is alkyl of from one to four carbon atoms, R, and

wherein R, is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formulai wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T,, T and T are each an independently selected alkyl group having from one to four carbon atoms; R,, R R R R, and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; (B) from 0 to about percent by weight based on the total weight of the fluid composition of an polyoxyalkylene glycol having a molecular weight of not less than l50 and. up to about 400, (C) from about 3 to about 43 percent by weight based on the total weight of the fluid of at least one diluent having the formula:

wherein R is alkyl of one to four inclusive carbon atoms, R is selected from the group consisting of hydrogen and alkyl of from one to four inclusive carbon atoms, x is an integer of from 2 to 4 inclusive and y is an integer of from 2 to 4 inclusive, (D) from about 0.05 to about 6.0 percent by weight, based on the weight of the total fluid, of an inhibitor for pH and corrosion control and (E) from about 0.001 to about 1.0 percent by weight of an antioxidant.

9. The hydraulic fluid composition of claim 8 wherein the said base or lubricant is:

10. The hydraulic fluid composition of claim 8 wherein the said polyoxyalkylene glycol is polyethylene glycol having a molecular weight of 300.

11. The hydraulic fluid composition of claim 8 wherein the said diluent is a mixture of triethylene glycol monomethyl ether and tetraethylene glycol monoethyl ether.

12. The hydraulic fluid composition of claim 8 wherein the said antioxidant is sodium nitrite.

13. The hydraulic fluid composition of claim 8 wherein the said inhibitor is a mixture of diethanolamine and tolutriazole.

14 The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in theapproximate percentage by weight indicated:

Percent by Weight lCH, (OCH,CH,),-,O],-B 67.39 Triethylene glycol monomethyl ether 23.20 Diethunolamine l. 7ll Polyethylene glycol (Mol. wt. 300) 7.62 Sodium nitrite 0.0l

15. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight lcHflocl-l CH hol -B 75.00 Triethylene glycol monomethyl ether 6.20 Tetraethylene glycol monoethyl ether 17.00 Diethanolamine L68 Tolutriazole 0.10 Sodium nitrite 0.02

16. The hydraulic fluid composition of claim 3 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight n( :)s la' 65.0 Tripropylene glycol dimethyl ether 22.9 N-ethyl morpholine 4.4 Polyethylene glycol (Mol. wt. 250) 7 7 17. The hydraulic fluid composition of claim 3 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight [CH, (OCH,CH,),,O ],,-B 67.04 Triethylene glycol monomethyl ether 21 .72 N-phenyl morpholine L89 Diethanolamine 0.85

Polyethylene glycol (Mol. wt: 300) 8.50

18. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent 19. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

'Percent by Weight lC,H.(OCH,CH,) Ol,-B 82.78 Triethylene glycol monoethyl ether l0.00 Methyldiethanolamine 2.20 Polyethylene glycol (Mol. Wt. 300) 5.00 Sodium nitrite 0.02

20. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight (CH,(OCH,CH,),O 1,-8 70.l3 Triethylene glycol monomethyl ether 20.00 Diethanolamine L86 Triethylene glycol (Mol. wt. I50) 8.00 Sodium nitrite 0.0l

21. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight ether 8.05 Polyethylene glycol (Mol. WI. 300) 6.11 Methyldiethanolamine L94 Sodium nitrite 0.03

22. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight [Borate Ester D] 80.46

O GHZCHZ MCH Tricthylene glycol monobutyl ether 1 L40 Diethanolumine 2.04 Polyethylene glycol (Mol. wt. 300) 6.08 Sodium nitrite 0.02

23. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated:

Percent by Weight Borate Ester [E] of the formula (c) prepared as described below: 29.18 cH oc|-i,CH,).10) .-B 55.43 Triethylene glycol monomethyl ether 1 1.9 Diethunolamine 0.9l Polyethylene glycol (Mol. wt. 300) 2.52 Sodium nitrite 0.0l

The borate ester of the formula (c) noted above is prepared by adding a random addition product of ethylene oxide, propylene oxide, and butyl alcohol to a mixture of toluene and ortho boric acid and heating the combined mixture to its boiling point.

24. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid a composition consisting essentially of from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition, of at least one borate ester selected from the group consisting of (a) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, 1: is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a borate ester of the formula:

wherein R is alkyl of from one to four carbon atoms, R and R are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with'the'proviso that one of R and R is methyl and one of R and R is hydrogen; (c) a borate ester of the formula:

wherein R, is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula:

wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula:

wherein T T and T are each an independently selected alkyl group having from one to four carbon atoms; R R R.;, R-,, R and R are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same.

t t t I! i fgggj UNlTED STATES PATENT OFFECE CERTIFICATE or CO EQTlN Inventor s Arthur W. Sawyer and David A. Csejka It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

I Col. 2, line 56, "(0113 (OCH2HCH3)2O)3-B" should read --(CH3(OCH2CHCH3)2O)3-B :ol. 2, line 57, "(C2H5(OCH2CHCH3)4O(3-B" should read --(C2H5(OCH2CHCH3)4O)3-B co1.5, line 5, "EH3(OCH2CH2)8(OCH2CHCH )5Q73-B should read -'-EH3 (ocH2cH2)8-(oc112c11cHs)s Q -B col.5, line 7, "16311 (,ocl-lzchcllsh -(ocllzchs) 1097-13 should read --Z s 7( 2 s) lO Z E) lo 7s- (301.3, line 64, that portion of the formula reading; "and O H (OCH CH )2-" should read --C H (OCH CH Col. 5, line 74, "500F. should read -550F.

Col. 6, line 22, "field" should read --fluid--.

Col. 12, line 45, Example XXVI]: under column of percent by weight, I "7. 500 should read --75. OO--.

Col. 15, line 10, Example XXX, "Z62H5(OCH2H2)3Q73-B" should read --Z 2H5( H2 H2)s Q7s- Col. 15, line 15 in Table 1, under column of test results. of Example I, "7.2 should read --l5. t.

Col. 15, line 21 in Table 1, under column of SAE 70125 specification, should read Col. 15, line 35 in Table 1, under column of test results. .of Example I, 0. 5 should read 0.05".

- See attached sheet alsof continued Certificate of Correction for U. S. Patent 5,625,899

001.20., Claim 24, line 38., "(R CHZCHR 6,(OCH CHR 0) -B" should read --(R -(OCH CHR2)n-= (OCH CHR -B 001.20, Claim 24, line 50, -(00320132) OCH2CHCH3)g-.) should read --E(OCH2CH2) (OCHgCHCH Y Signed and sealed this 1st day of Why 1973 (SAAL) Attest:

EDE-JARD M. FLETCHER; JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. A hydraulic fluid composition consisting essentially of (A) from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition of at least one base or lubricant selected from the group consisting of (a) borate ester of the formula: (R1(O-(CxH2x))y-O)3-B wherein R1 is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a borate ester of the formula: (R1-(OCH2CHR2)m-(OCH2CHR3)nO)3-B, wherein R1 is alkyl of from one to four carbon atoms, R2 and R3 are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R2 and R3 is methyl and one of R2 and R3 is hydrogen; (c) a borate ester of the formula: (R1(Rg)O)3-B, wherein R1 is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula: (-(OCH2CH2)r, (OCH2 CHCH3)s-), wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula: wherein T1, T2 and T3 are each an independently selected alkyl group having from one to four carbon atoms; R4, R5, R6, R7, R8 and R9 are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20 and with the proviso that in no more than two of the chains is the sum of n and M the same; (B) from 0 to about 20 percent by weight, based on the total weight of the fluid composition, of a polyoxyalkylene glycol having a molecular weight of not less than 150 and up to about 400, (C) from about 3 to about 43 percent by weight, based on the total weight of the fluid, of at least one diluent having the formula: R(O-(CH2)x)yOR'', wherein R is alkyl of one to four inclusive carbon atoms, R'' is selected from the group consisting of hydrogen and alkyl of from one to four inclusive carbon atoms, x is an integer of from 2 to 4 inclusive, and y is an integer of from 2 to 4 inclusive and (D) from about 0.5 to about 6.0 percent by weight, based on the total weight of the fluid of an inhibitor for pH and corrosion control.
 3. The hydraulic fluid composition of claim 2 wherein the said base or lubricant is: (CH3(OCH2CH2)3O)3-B.
 4. The hydraulic fluid composition of claim 2 wherein the said polyoxyalkylene compound is polyethylene glycol having a molecular weight of
 300. 5. The hydraulic fluid composition of claim 2 wherein the said diluent is a mixture of triethylene glycol monomethyl ether and tetraethylene glycol monoethyl ether.
 6. The hydraulic fluid of claim 2 wherein the said inhibitor is N-ethyl morpholine.
 7. The hydraulic fluid composition of claim 2 wherein the said inhibitor is a mixture of diethanolamine and tolutriazole.
 8. A hydraulic fluid composition consisting essentially of (A) from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition of at least one base or lubricant selected from the group consisting of (a) borate ester of the formula: (R1(O-(CxH2x))y-O)3-B wherein R1 is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a borate ester of the formula: (R1-(OCH2CHR2)m-(OCH2CHR3)nO)3-B, wherein R1 is alkyl of from one to four carbon atoms, R2 and R3 are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R2 and R3 is methyl and one of R2 and R3 is hydrogen; (c) a borate ester of the formula: (R1(Rg)O)3-B, wherein R1 is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula: (-(OCH2CH2)r, (OCH2CHCH3)s-), wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula: wherein T1, T2, and T3 are each an independently selected alkyl group having from one to four carbon atoms; R4, R5, R6, R7, R8 and R9 are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same; (B) from 0 to about 20 percent by weight based on the total weight of the fluid composition of an polyoxyalkylene glycol having a molecular weight of not less than 150 and up to about 400, (C) from about 3 to about 43 percent by weight based on the total weight of the fluid oF at least one diluent having the formula: R(O-(CH2)x)yOR'', wherein R is alkyl of one to four inclusive carbon atoms, R'' is selected from the group consisting of hydrogen and alkyl of from one to four inclusive carbon atoms, x is an integer of from 2 to 4 inclusive and y is an integer of from 2 to 4 inclusive, (D) from about 0.05 to about 6.0 percent by weight, based on the weight of the total fluid, of an inhibitor for pH and corrosion control and (E) from about 0.001 to about 1.0 percent by weight of an antioxidant.
 9. The hydraulic fluid composition of claim 8 wherein the said base or lubricant is: (CH3(OCH2CH2)3O)3-B.
 10. The hydraulic fluid composition of claim 8 wherein the said polyoxyalkylene glycol is polyethylene glycol having a molecular weight of
 300. 11. The hydraulic fluid composition of claim 8 wherein the said diluent is a mixture of triethylene glycol monomethyl ether and tetraethylene glycol monoethyl ether.
 12. The hydraulic fluid composition of claim 8 wherein the said antioxidant is sodium nitrite.
 13. The hydraulic fluid composition of claim 8 wherein the said inhibitor is a mixture of diethanolamine and tolutriazole.
 14. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (CH3(OCH2CH2)3O)3-B 67.39 Triethylene glycol monomethyl ether 23.20 Diethanolamine 1.78 Polyethylene glycol (Mol. wt. 300) 7.62 Sodium nitrite 0.01
 15. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (CH3(OCH2CH2)3O)3-B 75.00 Triethylene glycol monomethyl ether 6.20 Tetraethylene glycol monoethyl ether 17.00 Diethanolamine 1.68 Tolutriazole 0.10 Sodium nitrite 0.02
 16. The hydraulic fluid composition of claim 3 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (CH3(OCH2CH2)3O)3-B 65.0 Tripropylene glycol dimethyl ether 22.9 N-ethyl morpholine 4.4 Polyethylene glycol (Mol. wt. 250) 7.7
 17. The hydraulic fluid composition of claim 3 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (CH3(OCH2CH2)3O)3-B 67.04 Triethylene glycol monomethyl ether 21.72 N-phenyl morpholine 1.89 Diethanolamine 0.85 Polyethylene glycol (Mol. wt. 300) 8.50
 18. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (C4H9(OCH2CH2)2O)3-B44.68 (CH3(OCH2CH2)3O)3-B 31.63 Diethylene glycol monobutyl ether 3.81 Triethylene glycol monomethyl ether 11.05 Diethanolamine 1.83 Polyethylene glycol (Mol. wt. 300) 6.98 Sodium nitrite 0.02
 19. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (C2H5(OCH2CH2)3O)3-B 82.78 Triethylene glycol monoethyl ether 10.00 Methyldiethanolamine 2.20 Polyethylene glycol (Mol. wt. 300) 5.00 Sodium nitrite 0.02
 20. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (CH3(OCH2CH2)3O)3-B 70.13 Triethylene glycol monomethyl ether 20.00 Diethanolamine 1.86 Triethylene glycol (Mol. wt. 150) 8.00 Sodium nitrite 0.01
 21. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (C4H9(OCH2CH2)3O)3-B 28.29 (CH3(OCH2CH2)3O)3-B 55.58 Triethylene glycol monomethyl ether 8.05 Polyethylene glycol (Mol. wt. 300) 6.11 Methyldiethanolamine 1.94 Sodium nitrite 0.03
 22. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight (Borate Ester D)80.46
 23. The hydraulic fluid composition of claim 8 consisting essentially of the following ingredients in the approximate percentage by weight indicated: Percent by Weight Borate Ester (E) of the formula (c) prepared as described below: 29.18 (CH3(OCH2CH2)3O)3-B 55.48 Triethylene glycol monomethyl ether 11.9 Diethanolamine 0.91 Polyethylene glycol (Mol. wt. 300) 2.52 Sodium nitrite 0.01 The borate ester of the formula (c) noted above is prepared by adding a random addition product of ethylene oxide, propylene oxide, and butyl alcohol to a mixture of toluene and ortho boric acid and heating the combined mixture to its boiling point.
 24. In the operation of a fluid pressure operating device which uses hydraulic pressure transmission fluid, the improvement comprising using as said hydraulic pressure transmission fluid a composition consisting essentially of from about 54.5 to about 92 percent by weight, based on the total weight of the fluid composition, of at least one borate ester selected from the group consisting of (a) a borate ester of the formula: (R1(O-(CxH2x))y-O)3-B wherein R1 is alkyl of from one to four carbon atoms, x is an integer of from 2 to 4 and y is an integer of from 2 to 4; (b) a borate ester of the formula: (R1-(OCH2CHR2)m-(OCH2CHR3)nO)3-B, wherein R1 is alkyl of from one to four carbon atoms, R2 and R3 are independently selected from the group consisting of hydrogen and methyl, m and n are positive integers whose sum is from 2 to 20, and with the proviso that one of R2 and R3 is methyl and one of R2 and R3 is hydrogen; (c) a borate ester of the formula: (R1(Rg) O)3-B, wherein R1 is alkyl of from one to four carbon atoms, Rg is a heteric oxyalkylene chain of the formula: (-(OCH2CH2)r, (OCH2CHCH3)s-), wherein the sum of r and s is not more than 20 and wherein the weight percent of the oxyethylene units is not less than 20 based on the total weight of all the oxyalkylene units; and (d) a borate ester of the formula: wherein T1, T2 and T3 are each an independently selected alkyl group having from one to four carbon atoms; R4, R5, R6, R7, R8 and R9 are independently selected from the group consisting of hydrogen and methyl, n and m are positive integers independently selected in each chain and whose sum in each chain is from 2 to 20, and with the proviso that in no more than two of the chains is the sum of n and m the same. 